Ashkenazi Jewish ancestry is under the umbrella of European ancestry, but its clear from numerous studies that people of Ashkenazi ancestry are distinct from the European population at large. Most people with Ashkenazi ancestry trace their DNA to Eastern and Central Europe. But many also have Middle Eastern ancestry, which is just one reason for their genetic uniqueness.

Its clear that people with European ancestry are genetically distinct from those of Asian or African descent. What is less obvious is that genetic variation also exists within European groups. In these plots from a study by Elimear Kenny, you can see the genetic variation between major ancestral groups (left) and within a population (right). Jewish groups fall into the European cluster on the left. But people with Ashkenazi ancestry (blue) form a unique cluster that is largely distinct from Caucasian (CEU; green) and other Jewish populations (various colors) on the right. Individuals who are part Ashkenazi fall in between the Caucasian and Ashkenazi clusters.

The challenging history of Jewish groups has also contributed to their genetic uniqueness.

During the Jewish Diaspora or migration of Jewish people from the Middle East to other parts of the world the vast majority of Jewish individuals married and raised families within their faith. Many generations later this means that Ashkenazi Jews can appear more genetically related than they actually are.This genetic isolation has had important implications for health.

People with Ashkenazi ancestry are more likely to carry genetic factors that cause single-gene recessive Mendelian disorders where you need two bad copies of a gene to get the disease. Examples include Gaucher disease, Canavan disease, and Tay-Sachs disease. Because of this higher likelihood, screening for these genetic variants in prospective parents is standard practice for Jewish individuals starting families.

(23andMe tests for most mutations routinely screened in the Ashkenazi Jewish population for these conditions).

A number of multi-gene conditions are also more common in people with Ashkenazi ancestry. A multi-gene condition are conditions caused by genetic variation in a handful of genes.

One example is Crohns disease. People with Ashkenazi Jewish ancestry are two to four times as likely to develop Crohns compared Europeans in general. Although its not yet clear why the rates are higher in this population, its likely that genetic factors specific to Ashkenazi ancestry play a role.Knowing about your ancestry can teach you about your familys heritage and your risk for certain conditions. More knowledge means more informed decisions.

You can learn more about your ancestry and your genetic health with our Health + Ancestry service. Find out more here.